U.S. patent number 10,052,738 [Application Number 14/715,009] was granted by the patent office on 2018-08-21 for internal surface finishing apparatus and method.
This patent grant is currently assigned to United Technologies Corporation. The grantee listed for this patent is United Technologies Corporation. Invention is credited to Evan Butcher, Lexia Kironn, Joseph Ott, John P. Rizzo, Jr., Wendell V. Twelves, Jr..
United States Patent |
10,052,738 |
Twelves, Jr. , et
al. |
August 21, 2018 |
**Please see images for:
( Certificate of Correction ) ** |
Internal surface finishing apparatus and method
Abstract
An embodiment of an apparatus includes a centrifugal drive unit,
an arm assembly, an optional dynamic balancing ring, and a
workpiece fixture. The arm assembly is operatively connected to the
centrifugal drive unit and configured to revolve about a primary
axis perpendicular to the arm. The workpiece fixture is mounted to
the arm assembly, and is configured to rotate at least one
workpiece about at least one secondary axis outboard of the primary
axis.
Inventors: |
Twelves, Jr.; Wendell V.
(Glastonbury, CT), Rizzo, Jr.; John P. (Vernon, CT),
Butcher; Evan (Manchester, CT), Kironn; Lexia (Rocky
Hill, CT), Ott; Joseph (Enfield, CT) |
Applicant: |
Name |
City |
State |
Country |
Type |
United Technologies Corporation |
Hartford |
CT |
US |
|
|
Assignee: |
United Technologies Corporation
(Farmington, CT)
|
Family
ID: |
56120908 |
Appl.
No.: |
14/715,009 |
Filed: |
May 18, 2015 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20160339558 A1 |
Nov 24, 2016 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B24B
31/10 (20130101); B24B 31/006 (20130101); B24B
31/0218 (20130101) |
Current International
Class: |
B24B
31/00 (20060101); B24B 31/10 (20060101); B24B
31/02 (20060101) |
Field of
Search: |
;451/32,329
;366/217 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Lee5490. "Bolt Tumbler." YouTube. YouTube, Apr. 27, 2008. Web. Aug.
7, 2017. cited by examiner .
Extended European Search Report, for European Patent Application
No. 16170134.7, dated Sep. 23, 2016, 8 pages. cited by
applicant.
|
Primary Examiner: Hail; Joseph J
Assistant Examiner: Milanian; Arman
Attorney, Agent or Firm: Kinney & Lange, P.A.
Claims
The invention claimed is:
1. An apparatus comprising: a centrifugal drive unit; an arm
assembly operatively connected to the centrifugal drive unit and
configured to revolve about a primary axis perpendicular to the
arm; and a workpiece fixture mounted to the arm assembly, the
workpiece fixture includes at least one receptacle for receiving
and retaining a workpiece and processing media, and is configured
to rotate at least one workpiece about at least one secondary axis
outboard of the primary axis; wherein the arm assembly has an
adjustable length such that the arm assembly is configured to
revolve the workpiece fixture along a noncircular path about the
primary axis; and wherein the workpiece fixture comprises an open
gimbaled fixture or a gimbaled housing with at least one
enclosure.
2. The apparatus of claim 1, further comprising at least one
actuator connected to the arm assembly and configured to enable
out-of-plane rotation of the arm assembly and the workpiece
fixture.
3. The apparatus of claim 1, further comprising: a dynamic
balancing ring disposed at a junction of the centrifugal drive unit
and the arm assembly.
4. The apparatus of claim 1, wherein the workpiece fixture
comprises an elongated tumbling fixture.
5. The apparatus of claim 4, wherein the tumbling fixture includes
a wedge valve.
6. The apparatus of claim 1, further comprising: a transport
conduit disposed along the arm assembly, and connecting a media
reservoir and the workpiece fixture.
7. The apparatus of claim 1, wherein the arm assembly includes at
least one telescoping portion disposed between the workpiece
fixture and the primary axis.
8. The apparatus of claim 7, wherein the arm assembly includes at
least one cam follower in communication with a track disposed on or
about the centrifugal drive unit.
9. A method for processing a workpiece having at least one internal
passage, the method comprising: providing an open gimbaled fixture
or a gimbaled housing with at least one enclosure; providing loose
processing media within the internal passage of the workpiece;
revolving the workpiece around an external axis so as to accelerate
the processing media against one or more targeted internal surfaces
defining the internal passage; oscillating the workpiece during the
revolving step; orienting the workpiece to manipulate the loose
processing media relative to the one or more targeted surfaces; and
controlling the revolving step and the orienting step to uniformly
process the one or more targeted surfaces; wherein the orienting
step comprises: rotating the workpiece about at least one internal
axis outboard of the external axis via the open gimbaled fixture,
or the gimbaled housing with at least one enclosure.
10. The method of claim 9, wherein the media comprises at least one
of a transport agent and an abrasive agent.
11. The method of claim 9, wherein the orienting step comprises:
continuously rotating the workpiece about the at least one internal
axis.
12. The method of claim 9, wherein the orienting step comprises:
intermittently rotating the workpiece about the at least one
internal axis.
13. The method of claim 9, further comprising: exchanging at least
a portion of the processing media in the workpiece; and repeating
the revolving, orienting, and controlling steps.
14. The method of claim 9, wherein the revolving step comprises:
securing the workpiece to a centrifuge defining the external axis;
operating the centrifuge to move the workpiece around the external
axis; and dynamically balancing the centrifuge and the
workpiece.
15. The method of claim 9, further comprising: modifying a path of
the workpiece around the primary axis during the revolving step,
wherein the modifying step comprises: changing a distance of the
workpiece relative to at least one internal axis.
16. An apparatus comprising: a centrifugal drive unit; an arm
assembly operatively connected to the centrifugal drive unit and
configured to revolve about a primary axis perpendicular to the
arm; a workpiece fixture mounted to the arm assembly, the workpiece
fixture includes at least one receptacle for receiving and
retaining a workpiece and processing media, and is configured to
rotate at least one workpiece about at least one secondary axis
outboard of the primary axis; and at least one actuator connected
to the arm assembly and configured to enable out-of-plane rotation
of the arm assembly and the workpiece fixture.
17. The apparatus of claim 16, wherein the arm assembly is
configured to revolve the workpiece fixture along a circular path
about the primary axis.
18. The apparatus of claim 16, wherein the arm assembly has an
adjustable length such that the arm assembly is configured to
revolve the workpiece fixture along a noncircular path about the
primary axis.
19. The apparatus of claim 16, further comprising: a dynamic
balancing ring disposed at a junction of the centrifugal drive unit
and the arm assembly.
20. The apparatus of claim 16, wherein the workpiece fixture
comprises an open gimbaled fixture.
21. The apparatus of claim 16, wherein the workpiece fixture
comprises an elongated tumbling fixture.
22. The apparatus of claim 21, wherein the tumbling fixture
includes a wedge valve.
23. The apparatus of claim 16, wherein the workpiece fixture
comprises a gimbaled housing with at least one enclosure.
24. The apparatus of claim 16, further comprising: a transport
conduit disposed along the arm assembly, and connecting a media
reservoir and the workpiece fixture.
25. The apparatus of claim 16, wherein the arm assembly includes at
least one telescoping portion disposed between the workpiece
fixture and the primary axis.
26. The apparatus of claim 25, wherein the arm assembly includes at
least one cam follower in communication with a track disposed on or
about the centrifugal drive unit.
27. An apparatus comprising: a centrifugal drive unit; an arm
assembly operatively connected to the centrifugal drive unit and
configured to revolve about a primary axis perpendicular to the
arm; and a workpiece fixture mounted to the arm assembly, the
workpiece fixture includes at least one receptacle for receiving
and retaining a workpiece and processing media, and is configured
to rotate at least one workpiece about at least one secondary axis
outboard of the primary axis; wherein the arm assembly includes at
least one telescoping portion disposed between the workpiece
fixture and the primary axis; and wherein the workpiece fixture
comprises an open gimbaled fixture or a gimbaled housing with at
least one enclosure.
28. The apparatus of claim 27, wherein the arm assembly is
configured to revolve the workpiece fixture along a circular path
about the primary axis.
29. The apparatus of claim 27, wherein the arm assembly has an
adjustable length such that the arm assembly is configured to
revolve the workpiece fixture along a noncircular path about the
primary axis.
30. The apparatus of claim 27, further comprising at least one
actuator connected to the arm assembly and configured to enable
out-of-plane rotation of the arm assembly and the workpiece
fixture.
31. The apparatus of claim 27, further comprising: a dynamic
balancing ring disposed at a junction of the centrifugal drive unit
and the arm assembly.
32. The apparatus of claim 27, wherein the workpiece fixture
comprises an elongated tumbling fixture.
33. The apparatus of claim 32, wherein the tumbling fixture
includes a wedge valve.
34. The apparatus of claim 27, further comprising: a transport
conduit disposed along the arm assembly, and connecting a media
reservoir and the workpiece fixture.
35. The apparatus of claim 27, wherein the arm assembly includes at
least one cam follower in communication with a track disposed on or
about the centrifugal drive unit.
36. A method for processing a workpiece having at least one
internal passage, the method comprising: providing an open gimbaled
fixture or a gimbaled housing with at least one enclosure;
providing loose processing media within the internal passage of the
workpiece; revolving the workpiece around an external axis so as to
accelerate the processing media against one or more targeted
internal surfaces defining the internal passage; orienting the
workpiece to manipulate the loose processing media relative to the
one or more targeted surfaces, wherein the orienting step
comprises: rotating the workpiece about at least one internal axis
outboard of the external axis via the open gimbaled fixture, or the
gimbaled housing with at least one enclosure; controlling the
revolving step and the orienting step to uniformly process the one
or more targeted surfaces; and modifying a path of the workpiece
around the external axis during the revolving step, wherein the
modifying step comprises: changing a distance of the workpiece
relative to the external axis.
37. The method of claim 36, wherein the media comprises at least
one of a transport agent and an abrasive agent.
38. The method of claim 36, wherein the orienting step comprises:
continuously rotating the workpiece about the at least one internal
axis.
39. The method of claim 36, wherein the orienting step comprises:
intermittently rotating the workpiece about the at least one
internal axis.
40. The method of claim 36, further comprising: exchanging at least
a portion of the processing media in the workpiece; and repeating
the revolving, orienting, and controlling steps.
41. The method of claim 36, wherein the revolving step comprises:
securing the workpiece to a centrifuge defining the external axis;
operating the centrifuge to move the workpiece around the external
axis; and dynamically balancing the centrifuge and the
workpiece.
42. The method of claim 36, further comprising: oscillating the
workpiece during the revolving step.
Description
BACKGROUND
The disclosure relates generally to processing of workpieces and
more specifically to apparatus and methods for finishing internal
surfaces of said workpieces.
Workpieces with internal cavities can require internal surface
processing (roughening, smoothing, or introduction of compressive
stresses) but current apparatus and methods do not form reliable
and uniform application throughout the interior. Readily accessible
surfaces (e.g., within the line of sight) may be addressed with
machining, grinding, or a wide variety of abrasive media processes
to improve the surface finish. Currently, these processes are most
successful when applied to external surfaces and relatively short,
straight internal passages with constant cross sections.
Non-line-of-sight internal passages with serpentine paths and
irregularly shaped cavities are difficult or even impossible to
effectively polish. Turbine engine components are one example of
workpieces which contain such passages, and are subject to high
cycle fatigue (HCF) and low cycle fatigue (LCF) service
environments. The physics involved in additive manufacturing
deposition processes for metal, polymer, and ceramic components
results in a relatively rough, Ra 150 to Ra 1000 micro inches,
as-built surface finish. An improved surface finish in the range of
Ra 1 to Ra 125 micro inches can be required to avoid premature
cracking and part failure.
SUMMARY
An embodiment of an apparatus includes a centrifugal drive unit, an
arm assembly operatively connected to the centrifugal drive unit
and configured to revolve about a primary axis perpendicular to the
arm, and a workpiece fixture. The workpiece fixture is mounted to
the arm assembly, and is configured to rotate at least one
workpiece about at least one axis outboard of the primary axis.
An embodiment of a method for processing a workpiece having at
least one internal passage includes providing processing media
within the internal passage of the workpiece. The workpiece is
revolved around an external axis so as to accelerate the processing
media against one or more targeted internal surfaces defining the
internal passage. The workpiece is oriented to manipulate the
processing media relative to the one or more targeted surfaces. The
revolving step and the orienting step are controlled to uniformly
process the one or more targeted surfaces.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of a processing apparatus for a first
workpiece fixture.
FIG. 2A shows processing media in the workpiece mounted to the
first example embodiment of the workpiece fixture housing.
FIG. 2B depicts a workpiece fixture housing embodiment in an open
position.
FIG. 2C depicts the workpiece fixture housing embodiment in a
closed position.
FIG. 3A is a sectional view of a first example workpiece adapted to
contain processing media.
FIG. 3B shows a sectional view of a second example workpiece
adapted to contain processing media.
FIG. 4A is a schematic view of a workpiece processing apparatus
with a second workpiece fixture.
FIG. 4B is a schematic view of the workpiece shown in FIG. 4A.
FIG. 5A is a schematic of a processing apparatus with a third
workpiece fixture in a position for in-plane rotation.
FIG. 5B is a schematic of the processing apparatus and third
workpiece fixture in a position for out-of-plane rotation.
FIG. 6A shows details of the second workpiece fixture.
FIG. 6B shows details of manipulating a workpiece in the third
workpiece fixture.
FIG. 7 is an alternative embodiment, showing a media change system
incorporated into an arm assembly.
FIG. 8A shows a schematic example of an arm assembly configured to
provide a noncircular path for a workpiece fixture.
FIG. 8B is a detailed view of a configuration for incorporating the
workpiece fixture into an arm assembly having a noncircular
path.
FIG. 8C is a partial cutaway view of the workpiece fixture shown in
FIG. 8B.
FIG. 9 is a flowchart illustrating the steps of a method for
processing a hollow workpiece.
DETAILED DESCRIPTION
This disclosure generally teaches that an enhanced acceleration
field can increase the velocity, kinetic energy, and resultant
abrasive action of media against external and internal workpiece
surfaces. An apparatus and method utilize various particulates or
other media disposed in an internal workpiece passage (or
passages). The workpiece and particulates can be manipulated in a
multiaxis format to provide enhanced gravity to the particles for
both space-bound and earthbound processes. An accompanying fixture
can be capable of reorienting the workpiece(s) on an intermittent,
cyclical, or a continuous basis in a media flow field. Depending on
the location, an enhanced gravity field can register from about
0.01 G up to about 10,000 G. A more typical range of acceleration
values for earth bound industrial processes may be 1.01 G to 200 G.
The enhanced acceleration field can be realized with rotary motion,
linear motion, or a combination of both.
A centrifuge is the subject of an embodiment shown in FIG. 1. FIG.
1 shows assembly 10, and generally includes workpiece holding
fixture 12 secured to a distal end of arm or beam 14 operatively
connected to centrifugal drive unit 16. Arm 14 can be configured to
revolve about primary axis 18 passing therethrough. Here, arm 14
has a fixed length and thus results in a substantially circular
path for fixture 12 to revolve about primary axis 18. Centrifugal
drive unit 16 can include at least one motor (not visible) for
driving arm 14.
Workpiece holding fixture 12 can be configured to rotate at least
one workpiece (better seen in subsequent figures) about one or more
axes. In the example shown, gimbaled fixture 12 is secured to arm
14 via one or more attachments for rotation about one or more
outboard axes (secondary axes 20, 22). Fixture 12 and secondary
axes 20, 22 are thus configured to maintain the workpiece at an
outboard location along arm 14. FIG. 1 shows a receptacle for
receiving and retaining a workpiece. Here, that receptacle includes
workpiece housing 24 to secure the workpiece and processing media
(shown in FIGS. 2A-3B). Revolving fixture 12 via arm 14 accelerates
the workpiece and media contained therein, and results in an
enhanced gravity field applied to the workpiece and the media.
Though shown with a single fixture 12 and arm 14, it will be
appreciated that assembly 10 can be readily modified to include
multiple fixtures 12 and/or multiple arms 14 rotatable about
primary axis 18.
Dynamic balancing ring 26 can be disposed at a junction of
centrifugal drive unit 16 and arm 14, and is provided to compensate
for the changing positions of fixture 12, as well as the workpiece
and media (not shown in FIG. 1) during operation of assembly
10.
A workpiece can be reoriented with a single or a multi-axis
rotating fixture on either a continuous, semi-continuous, or
periodic basis to present one or more targeted surfaces to moving
media. Workpiece reorientation in the enhanced gravity field
(provided by a centrifuge or substantially equivalent device) may
be accomplished with constant velocity or intermittent rotary
motion around a single axis, around multiple axes, or combinations
thereof.
Here, fixture 12 is secured to arm 14 via clevis 28. One or both
gimbaled attachments may be motorized (via fixture motors 30A, 30B)
to drive selected orientations about one or both secondary axes 20,
22. Power for fixture motors 30A, 30B can be electrical, pneumatic,
hydraulic, or a gear or belt driven mechanism. If electric, power
can be supplied through a slip ring, an induction system,
batteries, or other suitable means.
Note that the fixture can be driven by a centrifuge or other
relatively simple, economical machine consisting of a frame, a
shaft, bearings, a drive motor, and an optional dynamic balancing
wheel. The frame may be designed to accommodate an overhung rotor
or a center hung rotor. The basic design of the centrifuge may be
readily scaled to accommodate large or small workpiece
families.
A programmable control module (PCM) 31 can be connected to provide
drive commands to assembly 10, controlling manipulation of the
workpiece and orientation and rotational velocity of the workpiece
around each axis (e.g., axes 18, 20, 22 in FIG. 1) during one or
more processing operations. Movement about each axis can be
mutually dependent or can be individually and independently
controlled. Coordination between two or more axes can target
selected workpiece surfaces and optimize the desired finishing
process for a specific workpiece geometry. The rotating workpiece
holding fixture(s) (e.g., fixture 12/housing 24) can also
incorporate a reciprocating or oscillating vibration mechanism (not
visible in FIG. 1) to further enhance the abrasive action of the
media particles in the enhanced acceleration field.
FIGS. 2A-2C illustrate one example configuration for fixturing and
manipulating a workpiece. FIG. 2A shows a partial view of workpiece
32. Workpiece housing 24 is shown in phantom to depict workpiece 32
retained in housing 24, which in turn is cut away to show media 36
in internal cavities 38. The example workpiece 32 has several
irregular, non line-of-sight passages which make it difficult to
access the internal surfaces defining them using conventional
techniques. Manipulation and orienting of workpiece 32 via housing
24 (and in general via apparatus 10) as described with respect to
FIG. 1 results in media traveling through these cavities 38,
contacting the defining internal surfaces to polish or otherwise
process them.
Generally, processing media can include, among other things, a
transport agent and/or an abrasive agent. The transport agent can
include a solid, a fluid, or a fluidized agent. Examples of
suitable transport fluids include pressurized gas (air or inert
gas), water, and mineral oil. The solid can be a metal, ceramic, or
polymer.
In one example, internal workpiece surfaces may be polished by
locating abrasive media within the cavities and passages of the
workpiece. As the workpiece is reoriented within the enhanced
acceleration field the sliding action of the media will polish the
surfaces it contacts. However, the apparatus and method are not
limited to polishing. In one non-limiting additional or alternative
step, metal shot can take the place of polishing media for peening
one or more interior surfaces, introducing residual compressive
stresses.
Candidate abrasive media materials for this process include any of
the common industrial abrasives. Typical media types can include
alumina (aluminum oxide), silicon carbide, silica (sand, glass
beads, or the like), diamond, garnet, metal (e.g., steel shot),
organic material (e.g., walnut shell). The size and shape of
individual media particles will be determined by the application.
The media may be wet or dry.
Work piece holding fixtures may have features such as internal
chambers and valves or external supply lines to control the
movement, evacuation, and replacement of abrasive media during the
surface finishing process. One example of such a system is shown in
FIG. 7.
FIG. 2B shows workpiece housing 24 with door 40 closed, showing
mounting brackets 42. In FIG. 2B, door 40 is closed so that
workpiece 32 (shown in FIG. 2A) is contained therein. Mounting
brackets 42 can be provided on the outside of housing 24 for
securing to arm 14 (e.g., via clevis 28 shown in FIG. 1). With
respect to FIG. 2C, workpiece housing 24 has door 40 open, showing
interior 43 for receiving and retaining workpiece 32 (shown in FIG.
2A). Brackets 42 can be incorporated into housing 24 in or around
door 40 in such a way as to allow access to interior 43 with
workpiece housing 24 remaining attached to arm 18 (shown in FIG.
1). Internal mounting devices (omitted for clarity) can be
contained in workpiece housing 24 to secure workpiece 32.
Alternatively, housing 24 can be sized so that it will securely
encompass workpiece 32, keeping it in place during operation and
manipulation.
FIGS. 3A and 3B show a manifold workpiece with two approaches for
enclosing processing media. FIG. 3A shows one example of manifold
workpiece 50 with end caps 52. Media 53 is manipulated against
internal workpiece surfaces 54 via enhanced gravity and orientation
about one or more axes as shown in other figures. FIG. 3B shows a
second example with passage extension 56 attached to manifold
workpiece 58, and can be handled in a similar manner so as to
process internal workpiece surfaces 60 with media 57.
It will be apparent that manipulation of workpieces with open ends
and irregular shapes can have some sort of enclosure to prevent
loss of media in use. Note that the path length and route the media
travels may be tailored with polymer or metal orifice cap
extensions which may dead end or loop around to another orifice to
create a continuous circuit. Custom tooling of this nature provides
additional options for managing media flow and abrasive action. The
first example may work best with an oscillating motion of fixture
12 (shown in FIG. 1), while the second example may work best with
rotational motion.
FIG. 4A shows an additional embodiment of fixture 12', mounted to
arm 14 via clevis 28. Here, fixture 12' includes an open gimbaled
fixture enclosure 24' with first receptacle portion 61A rotatable
about secondary axis 20 and second receptacle portion 61B rotatable
about secondary axis 22. For specific part families such as
manifold workpiece 62 shown in FIG. 4B, mounting in a fixture may
be simplified with external, removable mounting tabs 64 and
optional structural reinforcement. As such, manifold workpiece 62
can be mounted and secured directly to surfaces 66 of gimbaled
fixture enclosure 24'. Rotation about secondary axes 20, 22 can be
facilitated by motors 30A, 30B similar to that which is shown and
described with respect to FIG. 1. Media 68 is passed through
internal passages 70 in manifold workpiece 62 in a similar manner
as to other examples.
In one example, a workpiece is formed at least in part by one or
more additive manufacturing processes. In such a situation, the
mounting tabs or other surfaces can be co-grown with the workpiece
much like end caps and/or passage extensions in other examples.
FIGS. 5A and 5B illustrate a second embodiment of a processing
apparatus in two different operating modes. Apparatus 110 includes
tumbling workpiece fixture 112 mounted to arm assembly 114,
outboard of centrifuge unit 116. Similar to the arrangement shown
in FIG. 1, centrifuge unit 116 can include a motor (not visible)
for powering rotation of arm assembly 112 about primary axis 118 to
provide an enhanced gravity field (e.g., from 0.01 G to about
10,000 G in extremis, and more typically from 1.01 G to about 200 G
in earthbound applications).
Fixture 112 can include one or more attachments for mounting a
workpiece (not visible in FIGS. 5A and 5B) internally near or about
secondary axis 120. Here, housing 124 receives and retains a
workpiece for rotation about secondary axis 120 outboard of primary
axis 118. Apparatus 110 can also include dynamic balance ring 126
to facilitate enhanced gravity during simultaneous rotation about
axes 118 and 120.
Both external and internal work piece surfaces may be processed in
this type of fixture. As fixture 112 rotates end over end (about
secondary axis 120), loose media migrates under the influence of
the enhanced acceleration field from one end of the fixture to the
other, striking the workpiece located near the center (shown in
FIG. 6A-6B). Rotation can be actuated by a motor or other device
130. It will also be noted that tumbling fixture 112, or other
example fixtures can be adapted to include a plurality of
circumferentially spaced receptacles for retaining one or more
corresponding workpieces (e.g., workpieces 32, 132). The adapted
fixture tumbles similar to fixture 112 about axis 120, and
operation is reminiscent of a ferris wheel about one or more
secondary axes.
In the embodiment of arm assembly 114 shown in FIGS. 5A and 5B,
apparatus 110 can additionally or alternatively be configured to
provide out-of-plane rotation of fixture housing 124, and the
retained workpiece(s) during some or all of the surface processing
time. FIG. 5A shows arm assembly 114 in a configuration for
in-plane rotation of fixture 112, while FIG. 5B shows rotation of
fixture 112 in a nonplanar orientation. This can be achieved, for
example by operating actuator(s) 129 to lift and lower arm
extension 128 (i.e., control its yaw angle). With a constant yaw
angle, arm assembly 114 rotates in a plane substantially normal to
primary axis 118. And when the yaw angle is zero, distance of
fixture 112 from primary axis 118 is maximized, and linear velocity
of fixture 112 is minimized (for a given rotational velocity).
Linear velocity of fixture 112 can be increased by changing the yaw
angle of arm assembly 114 (e.g., via actuators 129) without
changing the rotational velocity of centrifuge unit 116. In
addition to control of motion about axes 118 and 120, process
control module 131 can be programmed or otherwise directed to
operate actuator(s) 129 in a manner to optimize the desired surface
processing. Actuators 129 or the equivalent can provide flexibility
to arm assembly 114 with at least one additional option to expedite
processing of hard-to-reach internal surfaces.
FIG. 6A illustrates a conceptual cross section of the elongated
hollow tumbling fixture housing 124 and FIG. 6B shows media
migration in housing 124 when controlled by a passive wedge valve
133. FIG. 6A shows passive valve 133 to control timing of when
media 136 is released toward workpiece 132 (with internal surfaces
138). In conjunction, the rotational velocity profile of the hollow
fixture housing 124 may also be tailored to optimize the release of
the abrasive media (over time, all at once, or in pulses).
Workpiece 132 can be fixed or movable to allow selected surfaces to
be presented to moving media 136 in a most favorable orientation
determined by its shape and the desired outcome. Additionally,
guide conduits can optionally be employed within the hollow fixture
to direct the media to specified surfaces. Both external and
internal surfaces can be processed simultaneously. Other valve
types may be used such as an active valve (see, e.g., FIG. 7).
FIG. 7 shows an embodiment of apparatus 210 and is described with a
dual-sided arm assembly 214 and a pair of fixtures 212A, 212B.
However, with appropriate balancing configurations, a single
fixture or more than two fixtures can be incorporated.
Fixtures 212A, 212B are operatively connected outboard of
centrifuge drive unit 216. Basic operation is similar to other
example embodiments, in which centrifuge drive unit rotates arm
assembly 214 about central or primary axis 218 to provide an
enhanced gravity field. Outboard fixtures 212A, 212B are also
rotatable about at least one secondary axis 220A, 220B outboard of
primary axis 218. Fixtures 212A, 212B can be secured via devises
228A, 228B and driven via motors 230A, 230B or equivalent (See FIG.
1 for example). Like other embodiments, a workpiece (not shown in
FIG. 7) can be enclosed within or otherwise secured to workpiece
fixture housings 224A, 224B which each include one or more
receptacles (not visible) for receiving and retaining corresponding
workpiece(s). In addition, optional actuators 232A, 232B change the
yaw angle of arm assembly 214, which in turn change the rotational
path of fixtures 212A, 212B and the attached workpiece in the
previously described manner. The centrifuge housing, dynamic
balance ring, and control module shown in other example embodiments
are omitted for clarity but suitable embodiments of these and other
elements can be assumed to be present unless otherwise stated.
FIGS. 6A and 6B showed a passive valve configuration which provide
for an economical approach to controlled or delayed introduction of
processing media. In FIG. 7, an active media change system is
incorporated into apparatus 210 to more completely control inlet
and outlet of various media into the fixture. This can enable
multi-step processing of internal surface(s) without having to
reposition the workpiece into another apparatus or housing.
Thus in addition to the above basic and optional elements, media
change assembly 234 can also be incorporated into this or other
embodiments. Here, various processing media can be stored in a
plurality of hoppers (e.g., hoppers 236A, 236B, 236C), flow of each
media controlled by a corresponding valve or plurality of valves
(e.g., valves 238A, 238B, 238C). Media is fed to union 240 which
can be disposed along or proximate to primary axis 218.
Media is transported from one or more of the hoppers to fixtures
212A, 212B (and the corresponding workpieces) by transport conduits
242A, 242B. Conduits 242A, 242B can generally be flexible metallic
or nonmetallic tubing depending on a particular application. In
certain limited embodiments, nonflexible tubing can be used where
there would be minimal bending or twisting stresses such as where
the yaw angle is fixed.
Since fixtures 212A, 212B are also rotatable about one or more
different axes (here, respective secondary axes 220A, 220B), a pair
of unions 244A, 244B can be provided at the outboard locations
adjacent to workpiece fixture housings 224A, 224B. Unions 240,
244A, and/or 244B can include centrifugal vanes (not shown) or
other suitable means for directing media to the respective
workpieces.
For each type of media, it can be evacuated from fixtures 212A,
212B through outlets 246A, 246B. These can include an opposing
discharge or dump valve, or additional unions adjacent to secondary
axes 220A, 220B. Selection of a particular type of outlet will
depend on whether the media will be continuously refreshed during
processing, or whether each step is performed on a batch basis.
Once the media is evacuated from fixtures 212A, 212B, additional
conduits (not shown) can direct used media away from apparatus 210
and the media can be reused, recycled, regenerated, or otherwise
suitably disposed of.
FIG. 8A is a partial sectional view of a portion of yet another
example embodiment, apparatus 310. This facilitates a noncircular
rotational path for one or more fixtures attached to arm assembly
314, and in turn, facilitates continuous variation of the enhanced
gravity field. In the example embodiment, a number of elements are
omitted for clarity but it will be appreciated that arm assembly
314 can be incorporated in place of other arm assemblies from other
example embodiments.
Arm assembly 314 includes telescoping sleeve portions 320A, 320B
disposed outboard of primary axis 318, and which are configured to
extend and retract radially relative to central arm portion 322. As
the unit is driven circumferentially by the centrifuge unit (not
shown in FIG. 8) about axis 318, cam followers 324A, 324B follow
the inside of noncircular track 326. This allows the length of arm
assembly 314 to be adjustable during operation so that one or more
workpiece fixtures will be subjected to variation in the enhanced
gravity field based on the constant rotational velocity and
continuously changing radial distance of the workpieces (not shown)
from primary axis 318. In an alternative embodiment, cam followers
324A, 324B and track 326 can be replaced or supplemented by linear
actuators (shown in previous figures) to allow for second order
changes in the enhanced gravity field.
FIG. 8B is an example in which fixture 312A is incorporated into
telescoping sleeve 320A. Here, fixture 312A and sleeve 320A are
supported at an outboard position by rails 328 and bearings 330
secured to central arm 322. Cam follower 324A is disposed at one
distal end of arm assembly 314 and runs along track 326 (shown in
FIG. 8A).
FIG. 8C is a cutaway and magnified view of a portion of FIG. 8B,
and shows fixture 312A and sleeve 320A with workpiece housing 334
disposed therein. Like other embodiments, workpiece housing 334 is
rotatable around one or more secondary axes (here axes 336 and
338). Housing 334 includes a receptacle for receiving and retaining
at least one workpiece which can be accessed, for example, through
door 340.
FIG. 9 shows steps of method 400 for processing internal surfaces
of a workpiece. Method 400 for processing a workpiece includes step
402, whereby loose processing media is provided within an internal
passage of a workpiece. As noted above, the media can be retained
in the passage(s) by caps, passage extensions, or other suitable
structures. The retention structures can be reusable or
sacrificial, and built along with the workpiece.
Processing media can include, among other things, a transport agent
and/or an abrasive agent. The transport agent can include a solid,
a fluid, or a fluidized agent. Examples of suitable transport
fluids include pressurized gas (air or inert gas), water, and
mineral oil. The solid can be a metal, ceramic, or polymer.
Abrasive media can be selected from a group including but not
limited to alumina, silicon carbide (SiC), silica, carbon, metal,
organic material, and combinations thereof.
With the media in place, step 404 can include revolving the
workpiece around a primary axis so as to accelerate the processing
media against one or more targeted internal surfaces defining the
internal passage. This provides an enhanced gravity field to the
workpiece (and processing media) as noted above. This step can take
place via centrifuge with a circular or noncircular path, as well
as a planar or nonplanar path. Rotation can be continuous or
intermittent, with constant or variable rotational velocity during
iteration(s) of step 404.
As part of step 406, the workpiece can be oriented to manipulate
the loose processing media relative to the one or more targeted
internal surfaces. For example, the workpiece can be mounted to or
secured within an enclosure or other suitable fixture/housing and
rotated about one or more secondary axes. The fixture/housing can
also be adapted to impart reciprocating, oscillating, or other
non-rotational motion to the workpiece and/or loose finishing
media. The fixture can be disposed at an outboard location and
rotatable about one or more secondary axes to reposition and
manipulate the processing media located therein. When step 406 is
done in conjunction with one or more iterations of revolving step
404 (either simultaneously or alternately), internal targeted
surfaces can be processed according to step 408.
As part of step 408, controlling the revolving step and the
orienting step to process the one or more targeted surfaces, a
processing control module or other device can provide commands to
the various motors and valves to provide a targeted surface with a
desired finish. In scenarios which have a high risk of fatigue, a
suitable surface roughness can be provided down to about Ra 16
microinches or less in some instances.
Optionally, step 410 includes iteratively repeating one or more of
the above steps. For example, it may be that progressively finer
grit may be needed to achieve the desired result. Additionally or
alternatively, different internal surfaces (in the same or
different passage) could require different parameters. As such, the
processing media can be periodically moved and/or exchanged
manually or automatically.
This apparatus and method are anticipated to be useful in a variety
of manufacturing scenarios. One expected area of use is in
conjunction with additive-manufactured high temperature materials
such as those in turbine engine applications. A relatively rough
surface finish with an attendant fatigue life reduction is an
inherent feature of current additive manufacturing processes.
Enabling directed, aggressive abrasive media action on both
external and internal work piece passage surfaces such as walls,
struts, ribs, fillets, and cavities will significantly open the
turbine engine design space for components fabricated with additive
manufacturing. The low cost of the apparatus combined with the
accelerated abrasion rate this process offers means that rapid, low
cost part finishing may be realized.
Discussion of Possible Embodiments
The following are non-exclusive descriptions of possible
embodiments of the present invention.
An embodiment of an apparatus includes a centrifugal drive unit, an
arm assembly operatively connected to the centrifugal drive unit
and configured to revolve about a primary axis perpendicular to the
arm, and a workpiece fixture. The workpiece fixture is mounted to
the arm assembly, and is configured to rotate at least one
workpiece about at least one axis outboard of the primary axis.
The apparatus of the preceding paragraph can optionally include,
additionally and/or alternatively, any one or more of the following
features, configurations and/or additional components:
An apparatus according to an exemplary embodiment of this
disclosure, among other possible things includes a centrifugal
drive unit; an arm assembly operatively connected to the
centrifugal drive unit and configured to revolve about a primary
axis perpendicular to the arm; and a workpiece fixture mounted to a
distal end of the arm assembly, the workpiece fixture includes at
least one receptacle for receiving and retaining a workpiece and
processing media, and is configured to rotate at least one
workpiece about at least one secondary axis outboard of the primary
axis.
A further embodiment of the foregoing apparatus, wherein the arm
assembly is configured to revolve the workpiece fixture along a
circular path about the primary axis.
A further embodiment of any of the foregoing apparatus, wherein the
arm assembly has an adjustable length such that the arm assembly is
configured to revolve the workpiece fixture along a noncircular
path about the primary axis.
A further embodiment of any of the foregoing apparatus, wherein the
apparatus further comprises at least one actuator connected to the
arm assembly and configured to enable out-of-plane rotation of the
arm assembly and the workpiece fixture.
A further embodiment of any of the foregoing apparatus, wherein the
apparatus further comprises a dynamic balancing ring disposed at a
junction of the centrifugal drive unit and the arm assembly.
A further embodiment of any of the foregoing apparatus, wherein the
workpiece fixture comprises an open gimbaled fixture.
A further embodiment of any of the foregoing apparatus, wherein the
workpiece fixture comprises an elongated tumbling fixture.
A further embodiment of any of the foregoing apparatus, wherein the
tumbling fixture includes a wedge valve.
A further embodiment of any of the foregoing apparatus, wherein the
workpiece fixture comprises a gimbaled housing with at least one
enclosure.
A further embodiment of any of the foregoing apparatus, wherein the
apparatus further comprises a transport conduit disposed along the
arm assembly, and connecting a media reservoir and the workpiece
fixture.
A further embodiment of any of the foregoing apparatus, wherein the
arm assembly includes at least one telescoping portion disposed
between the workpiece fixture and the primary axis.
A further embodiment of any of the foregoing apparatus, wherein the
arm assembly includes at least one cam follower in communication
with a track disposed on or about the centrifugal drive unit.
An embodiment of a method for processing a workpiece having at
least one internal passage includes providing processing media
within the internal passage of the workpiece. The workpiece is
revolved around an external axis so as to accelerate the processing
media against one or more targeted internal surfaces defining the
internal passage. The workpiece is oriented to manipulate the
processing media relative to the one or more targeted surfaces. The
revolving step and the orienting step are controlled to uniformly
process the one or more targeted surfaces.
The method of the preceding paragraph can optionally include,
additionally and/or alternatively, any one or more of the following
features, configurations and/or additional components:
A method according to an exemplary embodiment of this disclosure,
among other possible things includes providing loose processing
media within the internal passage of the workpiece; revolving the
workpiece around an external axis so as to accelerate the
processing media against one or more targeted internal surfaces
defining the internal passage; orienting the workpiece to
manipulate the loose processing media relative to the one or more
targeted surfaces; and controlling the revolving step and the
orienting step to uniformly process the one or more targeted
surfaces.
A further embodiment of the foregoing method, wherein the media
comprises at least one of a transport agent and an abrasive
agent.
A further embodiment of any of the foregoing methods, wherein the
orienting step comprises continuously rotating the workpiece about
at least one internal axis.
A further embodiment of any of the foregoing methods, wherein the
orienting step comprises intermittently rotating the workpiece
about at least one internal axis.
A further embodiment of any of the foregoing methods, wherein the
method further comprises: exchanging at least a portion of the
processing media in the workpiece; and repeating the revolving,
orienting, and controlling steps.
A further embodiment of any of the foregoing methods, wherein the
revolving step comprises: securing the workpiece to a centrifuge
defining the external axis; operating the centrifuge to move the
workpiece around the external axis; and dynamically balancing the
centrifuge and the workpiece.
A further embodiment of any of the foregoing methods, wherein the
method further comprises oscillating the workpiece during the
revolving step.
A further embodiment of any of the foregoing methods, wherein the
method further comprises modifying a path of the workpiece around
the primary axis during the revolving step, wherein the modifying
step comprises changing a distance of the workpiece relative to the
second axis.
While the invention has been described with reference to an
exemplary embodiment(s), it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment(s) disclosed, but that the invention will
include all embodiments falling within the scope of the appended
claims.
* * * * *